Recessed compensating sheave

ABSTRACT

A compensating sheave arrangement used in an elevator system permits the use of both a single counterweight buffer and a single elevator car buffer, notwithstanding the compensated rope segments on either side of the compensating sheave are vertically disposed and apply non-eccentric forces on both the car and the counterweight. A recessed compensating sheave is used having a recess dimensioned so as to form vertical passages on each side thereof, the passage on one side receiving the car buffer and on the other, the counterweight buffer. The sheave is designed so as to have its pitch diameter substantially equal to the horizontal distance between the vertical axis of the car and the vertical axis of the counterweight and thereby result in an arrangement whereby the compensating rope segments ascending from the sheave are substantially vertically disposed.

' United States Patent 1 Cilderman et al. I

[in 3,739,881 June 19, 1973 RECESSED COMPENSATING SHEAVE [7 5] Inventors: Janis Cilderman, Teaneck, N.J.;

. 1 Charles Heyd Clarkson, Madeira Beach, Fla.

[73] Assignee: Otis Elevator Company, New York,

22 Filed: June 12, 1972 211 Appl. No.: 261,678

FOREIGN PATENTS OR APPLICATIONS 1,558,090 3/1968 France 187/89 ir q tqm fl rfis y iqrnsby Attorney-Joseph L. Sharon and Siegmar Silber 57 ABSTRACT A compensating sheave arrangement used in an elevator system permits the use of both a single c0unter weight buffer and a single elevator car buffer, notwithstanding the compensated rope segments on either side of the compensating sheave are vertically disposed and apply non-eccentric forces on both the car and the counterweight. A recessed compensating sheave is used having a recess dimensioned so as to form vertical passages on each side thereof, the passage on one side receiving the car buffer and on the other, the counterweight buffer. The sheave is designed so as to have its pitch diameter substantially equal to the horizontal distance between the vertical axis of the car and the vertical axis of the counterweight and thereby result in an arrangement whereby the compensating rope segments ascending from the sheave are substantially vertically disposed.

6 Claims, 6 Drawing Figures l REQESSED COMPENSATING SHEAVE This invention relates to elevators and more particularly to an improved sheave for use with elevator compensating ropes.

Traction elevator installations which exceed a predetermined rise are provided typically with compensating ropes which interconnect the undersides of the elevator car and its counterweight and depend to the bottom of the hoistway. These compensating ropes are of substantially the same weight as the hoisting ropes. Consequently, as the elevator car moves on a trip from one landing to another and the hoisting ropes are driven from one side of the drive sheave to the other thereby changing the load they present to the hoisting machine, a substantially equal compensating weight is added to the opposite side of the sheave by the compensating ropes so that the load presented to the hoisting machine remains substantially constant during the trip.

Rotatably mounted in the bights of the compensating ropes is a compensating sheave. The weight of this sheave provides tensioning for the compensating ropes. Its dimensions are suitably chosen to enable the compensating ropes to be aligned vertically and at the same time to be connected to the undersides of the car and counterweight in such a manner as to prevent the ropes from applying eccentric loads to those elements. Such loads are desirably avoided because they produce thrust forces on the guide shoes which can detract from the riding quality of elevators. A suitable manner of connecting compensating ropes to car and counterweight and avoiding eccentric loads is to connect the compensating ropes so that the net effect of the compensating weight acts through a point on the car mid way between the car rails and through a point on the counterweight midway between the counterweight rails.

The foregoing roping arrangement poses a problem with regard to the accommodation of the buffers at the bottom of the hoistway. The carand counterweight buffers are positioned in the pit so that in the event of overtravel they bring the car and counterweight to a stop in a balanced manner without lurching or dipping in any direction. This is accomplished by having the buffers effectively apply a stopping force to the car and counterweight at the points midway between the respective guide rails. Thus, if single buffers were to be used under both the car and counterweight, they would occupy the same space as would be occupied by the compensating sheave and ropes in the forementioned suitable roping arrangement. In the past this dilemma was avoided by employing compensating sheaves which were smaller than the distance from the midpoint between the car rails to the midpoint between the counterweight rails. The ropes ascending from such compensating sheaves, however, produce eccentric loading either by being somewhat out of vertical alignment or by being attached so that the effect of the compensating weight is at a point other than midway between the guide rails. An alternative approach employs a largediameter sheave and places two buffers under both the car and counterweight. Each set of these buffers is arranged one on each side of the compensating sheave appropriately spaced between the guide rails to stop the respective car or counterweight in a balanced man ner. This alternative, however, is less economical in terms of installation time and materials than single buffer installations.

It is an object of the present invention to provide an improved compensating sheave.

Another object is to provide a traction elevator system with a compensating sheave which permits the use of both a single counterweight buffer and a single elevator car buffer notwithstanding the compensating rope segments on either side of the compensating sheave are vertically disposed and apply non-eccentric forces on both the car and the counterweight.

A feature of the present invention is that the compensating sheave has a groove therein forming passages on either side for housing car and counterweight buffers.

The invention is practiced in an elevator installation in which an elevator car and counterweight are suspended in a hoistway by a traction drive means. A car buffer is mounted beneath the car at the bottom of the hoistway so as to prevent the downward overtravel of the car and so that the vertical centerline of the car buffer is coincident with the vertical axis of the car. A counterweight buffer is mounted beneath the counterweight so as to prevent the downward overtravel of the counterweight and so that the vertical centerline of the counterweight buffer is coincident with the vertical axis of the counterweight. This prevents downward overtravel of the counterweight. One or more pairs of compensating ropes, each being substantially equal in length, interconnect the car and counterweight. Of each rope, one end is attached to the car; the other, to the counterweight; and the intermediate portion forms a loop depending to the lower end of the hoistway. At the bottom of the hoistway, a compensating sheave is rotatably mounted on a horizontally disposed shaft. Every pair of ropes has, located midway between the longitudinal axes of each pair of ropes, a common vertical plane to which the axis of the shaft of the compensating sheave is normal and which plane includes the vertical axes of the car and counterweight. The rim of the compensating sheave has two outermost or side portions and a centermost portion of which the outermost portions have an equal number of rope grooves and the centermost portion has arecess or groove dimensioned to receive the car and counterweight buffers. Each rope groove receives the bight of a compensating rope, and the buffer groove forms a vertical passageway on each side of the sheave which is so dimensioned as to receive the respective'car and counterweight buffers.

Other objects, features and advantages will be apparent to those skilled in the elevator art from the following description when considered in conjunction with the appended claims and accompanying drawing, in which:

FIG. I is a plan view of a prior art pit layout for sin- 'gle-buffer installations;

FIG. 2 is a plan view of a ble-buffer installations;

FIG. 3 is a plan view of a pit layout using the present invention;

FIG. 4 is a simplified elevation view of the compensating sheave as it would appear at the bottom of a hoistway;

FIG. 5 is a sectional view with parts removed taken along line -5 of FIG. 4; and

FIG. 6 is a cross-sectional view with parts removed talten along line 6-6 of FIG. 4.

prior art pit layout for dou- Referring to FIGS. 1, 2 and 3, the prior art arrangements are compared to the present arrangement. In these figures, the larger dashed rectangle represents the projected cross-section of an elevator car platform; and the smaller dashed rectangle, that of an associated counterweight. The relative position of respective rail guides are shown for each car and counterweight.

FIG. 1 shows a single buffer installation with a compensation roping arrangement employed with low to medium speed elevators. It should be clear that vertically ascending ropes from a smaller sheave 10, located midway between buffers 1 1 and 12, mounted under the car and the counterweight, produce eccentric loading on both the car and the counterweight. On the other hand, the prior art use of a large-diameter sheave, such as 13 in FIG. 2, provided balanced compensating roping for high-speed elevators; but this arrangement requires four buffers (14, 15, 16 and 17) for balanced overtravel stopping. The arrangement of FIG. 3 includes a large-diameter recessed sheave 21 in accordance with the present invention with single buffers 18 and 19 for the car and counterweight.

Referring now to FIG. 4, the bottom of an elevator hoistway 20 is shown in which compensating sheave 21 is mounted in typical fashion. Sheave 21 is retained between rails 22 (FIG. 5) and is rotatably mounted in any suitable manner on horizontally disposed shaft 23 in frame members 24 which cooperate with rails 22 and with a typical hold-down device (not shown). Viewing sheave 21 from above as in FIG. 5, it can be seen to be spool-like in construction having a rim with two outermost portions 25 and a centermost portion 26. As can most clearly be seen in the cross-sectional view in FIG. 6, the outermost portions each have an equal number of rope grooves 27 in the peripheral surface thereof. In

the embodiment shown there is one groove 27 in each said outermost portion 25; however, any suitable number may be employed. These grooves receive compensating ropes 28 (FIG. 4) which are arranged in pairs with the members of each pair being on opposite sides of the above described centermost portion 26 and equidistant therefrom.

Compensating ropes 28 are each substantially equal in length and each ascends from compensating sheave 21 to the underside of the car (not shown) where its one end is connected and to the underside of the counterweight (not shown) where its other end is connected. Upon being so connected, ropes 28 have intermediate portions depending in loops to the lower end of hoistway 20, the bights of such loops being received in grooves 27. These intermediate portions also include rope segments 31 (FIG. 4) which depend from the elevator car and rope segments 32 which depend from the counterweight.

In order to prevent eccentric loading on the car or counterweight upon the connection of segments 31 and 32, the pitch diameter, that is, the diameter of each rope groove 27 of sheave 21 as measured between the centers of rope segments 31 and 32 of each rope, is made equal to the horizontal distance between the vertical axis 33 (FIG. 4) of the car and the vertical axis 34 of the counterweight. By the term vertical axis of the car and counterweight is meant the imaginary vertical line coextensive with the car and counterweight, respectively, and passing through the midpoint of the horizontal line between the respective guide rails provided for the car and counterweight.

Sheave 21 is so mounted in the elevator pit that each rope segment 31, on the car side, is vertical and the longitudinal axes of all are coplanar with each other and with vertical axis 33 of the car which is located midway between the rope segments. Similarly, each segment 32, on the counterweight side, is vertical and the longitudinal axes of all are coplanar with each other and with vertical axis 34 of the counterweight which is located midway between the rope segments. In this arrangement, vertical axes 33 and 34 can be viewed as lying within a vertical plane which axially bisects the sheave 21 and has shaft 23 normal thereto. This same vertical plane is parallel to the planes formed by the longitudinal axes of compensating ropes 28 and is midway between each of the forementioned pairs of such ropes.

The recesses, or passages, formed by centermost portion 26 and outermost portions 25 of sheave 21 are of dimensions which provide adequate housing both for car buffer 18 (FIG. 4) mounted beneath the car at the bottom of hoistway 20 and for counterweight buffer 19. This latter buffer may suitably be mounted either on the underside of the counterweight or beneath the counterweight at the bottom of hoistway 20. Where, as shown in FIG. 4, the counterweight buffer is of the type mounted on the underside of the counterweight, bumper 35 for cooperation with counterweight buffer 19 is mounted at the bottom of the hoistway. Each buffer 18 and 19 is located so that its vertical centerline coincides with the respective vertical axis of the component with which it cooperates. In this way, both the car and counterweight can be brought to a stop by their respec tive buffers in the event of downward overtravel in a balanced manner, i.e., without either lurching or dipping in any direction.

From the foregoing, it will be understood that this compensating sheave provides a recess dimensioned as to receive the respective car and counterweight buffers. There is provided a sheave with the ropes ascending vertically therefrom and attaching to the underside of the car and counterweight, respectively, without applying eccentric forces and allowing single buffers.

While the present invention has been described in a preferred embodiment, it will be obvious to those skilled in the art that various modifications can be made therein within the scope of the invention. It is intended that the appended claims cover all such modifications.

What is claimed is:

l. The combination of an elevator car and counterweight, which are suspended in a hoistway by traction drive means, with a car buffer mounted beneath said car at the bottom of said hoistway and preventing downward overtravel of said car, a counterweight buffer mounted beneath said counterweight with the vertical centerline of said counterweight buffer coincident with the vertical axis of said counterweight, said counterweight buffer preventing downward overtravel of said counterweight, at least one pair of compensating ropes, each said rope being of substantially equal length, one end of each said rope being attached to the underside of said car and the other end being attached to the underside of said counterweight, each said rope forming a loop depending to the lower end of said hoistway, and a compensating sheave rotatably mounted on a horizontally disposed shaft at the bottom of said hoistway, the axis of said shaft being substantially normal to the vertical plane located substantially midway between the longitudinal axes of the ropes of each pair of ropes, said plane including therein the vertical axes of said car and said counterweight, said sheave having a rim with two outermost portions and a centermost portion, said outermost portions each having an equal number of rope grooves each receiving the bight of one of said ropes, said centermost portion of said rim having a buffer groove forming a first vertical passage on one side of said sheave dimensioned to receive said car buffer and a second vertical passage on the opposite side of said sheave dimensioned to receive said counterweight buffer.

2. The combination according to claim 1, wherein each one of said ropes includes a first rope segment between the underside of said car and said sheave, said first rope segments having the longitudinal axes thereof coplanar with the vertical axis of said car.

3. The combination according to claim 2, wherein each one of said ropes includes a second rope segment between the underside of said counterweight and said sheave, said second rope segments having the longitudinal axes thereof coplanar with the vertical axis of said counterweight.

4. The combination according to claim 1, wherein the rope grooves in said sheave have a pitch diameter substantially equal to the horizontal distance between the vertical axis of said car and the vertical axis of said counterweight.

5. The combination according to claim 4, wherein said car buffer is mounted at the bottom of said hoistway so that the vertical centerline of said car buffer coincides with the vertical axis of said car.

6. An improved elevator system of the type wherein a car and a counterweight are suspended in a hoistway by traction drive means, wherein a plurality of compen sating ropes with longitudinal axes in parallel planes interconnect the underside of said car and the underside of said counterweight, said compensating ropes being of substantially equal lengths and having intermediate portions forming loops depending to the lower end of said hoistway, and wherein buffer means prevent overtravel of said car and said counterweight, said buffer means including a buffer for said car mounted beneath said car at the bottom of said hoistway and a buffer for said counterweight mounted beneath said counterweight, the improvement comprising, a spool-like compensating sheave for tensioning said ropes, said sheave being disposed in the bights of said ropes, said sheave having a rim with two outermost portions and an innermost portion, the outermost portions being of larger diameter than the innermost portion, said sheave being aligned with the axis of its shaft normal to the plane including the vertical axis of said car and the vertical axis of said counterweight, each said outermost portion having an equal number of rope grooves in the peripheral surface thereof, said grooves having a pitch diameter equal to the horizontal distance between the vertical axis of said car and the vertical axis of said counterweight, said innermost portion forming a first sheave recess at the bottom of said hoistway in line with the downwardly extended vertical axis of said car and a second sheave recess at the bottom of said hoistway in line with the downwardly extended vertical axis of said counterweight, said recesses being sufficiently dimensioned for receiving therein said buffer means for said car and said counterweight. 

1. The combination of an elevator car and counterweight, which are suspended in a hoistway by traction drive means, with a car buffer mounted beneath said car at the bottom of said hoistway and preventing downward overtravel of said car, a counterweight buffer mounted beneath said counterweight with the vertical centerline of said counterweight buffer coincident with the vertical axis of said counterweight, said counterweight buffer preventing downward overtravel of said counterweight, at least one pair of compensating ropes, each said rope being of substantially equal length, one end of each said rope being attached to the underside of said car and the other end being attached to the underside of said counterweight, each said rope forming a loop depending to the lower end of said hoistway, and a compensating sheave rotatably mounted on a horizontally disposed shaft at the bottom of said hoistway, the axis of said shaft being substantially normal to the vertical plane located substantially midway between the longitudinal axes of the ropes of each pair of ropes, said plane including therein the vertical axes of said car and said counterweight, said sheave having a rim with two outermost portions and a centermost portion, said outermost portions each having an equal number of rope grooves each receiving the bight of one of said ropes, said centermost portion of said rim having a buffer groove forming a first vertical passage on one side of said sheave dimensioned to receive said car buffer and a second vertical passage on the opposite side of said sheave dimensioned to receive said counterweight buffer.
 2. The combination according to claim 1, wherein each one of said ropes includes a first rope segment between the underside of said car and said sheave, said first rope segments having the longitudinal axes thereof coplanar with the vertical axis of said car.
 3. The combination according to claim 2, wherein each one of said ropes includes a second rope segment between the underside of said counterweight and said sheave, said secoNd rope segments having the longitudinal axes thereof coplanar with the vertical axis of said counterweight.
 4. The combination according to claim 1, wherein the rope grooves in said sheave have a pitch diameter substantially equal to the horizontal distance between the vertical axis of said car and the vertical axis of said counterweight.
 5. The combination according to claim 4, wherein said car buffer is mounted at the bottom of said hoistway so that the vertical centerline of said car buffer coincides with the vertical axis of said car.
 6. An improved elevator system of the type wherein a car and a counterweight are suspended in a hoistway by traction drive means, wherein a plurality of compensating ropes with longitudinal axes in parallel planes interconnect the underside of said car and the underside of said counterweight, said compensating ropes being of substantially equal lengths and having intermediate portions forming loops depending to the lower end of said hoistway, and wherein buffer means prevent overtravel of said car and said counterweight, said buffer means including a buffer for said car mounted beneath said car at the bottom of said hoistway and a buffer for said counterweight mounted beneath said counterweight, the improvement comprising, a spool-like compensating sheave for tensioning said ropes, said sheave being disposed in the bights of said ropes, said sheave having a rim with two outermost portions and an innermost portion, the outermost portions being of larger diameter than the innermost portion, said sheave being aligned with the axis of its shaft normal to the plane including the vertical axis of said car and the vertical axis of said counterweight, each said outermost portion having an equal number of rope grooves in the peripheral surface thereof, said grooves having a pitch diameter equal to the horizontal distance between the vertical axis of said car and the vertical axis of said counterweight, said innermost portion forming a first sheave recess at the bottom of said hoistway in line with the downwardly extended vertical axis of said car and a second sheave recess at the bottom of said hoistway in line with the downwardly extended vertical axis of said counterweight, said recesses being sufficiently dimensioned for receiving therein said buffer means for said car and said counterweight. 